This invention generally relates to cartridge-type dental injectors, and more particularly, to a mounting device for a barrel adapted to receive a cartridge therein.
In a manual type dental injection device, a cartridge receiving barrel is secured to a body of the injection device by fastening means such as a cramping screw. The barrel is also provided with diametrically opposite viewing windows formed therein and having a sufficient size to insert the cartridge into the barrel. In case of an electrically powered dental injection device, a cartridge receiving barrel is removably mounted in a socket defined by a mounting member which is connected to a support member for a plunger rod, the support member being secured to a nose portion of a housing of the injection device. The barrel is removed from the socket after completion of injection so that the cartridge can be inserted in the barrel, and the barrel is again mounted in the socket for injection. The barrel is provided with diametrically opposite viewing windows.
It is well known that the cartridge includes a rubber plug retained at the end of the cartridge by a metallic cap for sealing and adapted to be penetrated with an needle of a needle fitting when it is threadedly secured to the barrel at its forward end, and a plunger rubber fitted in a rear open end of the cartridge, and adapted to be pushed by the plunger rod, thereby ejecting the injection liquid contained in the cartridge, through the needle.
In the injection device of either type, the viewing windows play a important role in enabling a condition of the cartridge to be visibly ascertained, that is to say, enabling it to be determined how much injection liquid in the cartridge has been injected therefrom. The needle has at the tip end a cut surface to provide a sharp cutting edge thereto, and it is required that the gums be pierced with the sharp cutting edge with the cut surface facing the teeth of a patient.
As each dentist has a particular physique or posture for treatment to a patient, this results in an angle at which the dentist can best view the cartridge through the viewing window being changed. It is therefore required that a dentist alters an angular position of the viewing window in the barrel to one at which it is easy for the dentist to view the cartridge in the barrel through the viewing window, as well as the orientation of the cut surface defining the sharp cutting edge of the needle, against the teeth. In the case of manual type injector, the cramping screw is loosened relative to the injector body to enable the angular position of the barrel to be altered, but such manual operations for loosening and then tightening the cramping screw are troublesome and inefficient. In the case of the electrically powered dental injection device, it is impossible to alter the orientation of the viewing window so that it is oriented with the cut surface of the needle, because the barrel is installed in the socket at a fixed position. Since the barrel is arranged to enable it to be removed from the socket whenever it is to be loaded with the cartridge, there is a need for a simplified arrangement for installing the barrel in the socket.
It is an object of the invention to provide a cartridge type dental injection device capable of easily altering the orientations of the viewing window and of the cut surface of the needle as desired.
This object of the invention can be achieved by providing a device for mounting cartridge receiving barrel in a cartridge type dental injection device comprising a mounting member having a socket, a barrel adapted to be inserted in the socket and having diametrically opposite viewing windows formed therein, the mounting member having a plurality of circumferentially spaced apart ball retaining holes, and a locking ball placed in each of the holes, the barrel being provided with an annular groove adapted to receive a portion of each locking ball therein, and a locking ring having an annular cam surface and a relieving surface positioned adjacent to each other and movable between a position where when the locking balls are in alignment with the annular groove, the annular cam surface pushes the locking balls toward the annular groove to bring portions of the locking balls into engagement with the annular groove and a position where the relieving surface faces the locking balls to release them from the annular groove.
According to the invention, the movement of the locking ring from the position where the locking balls are released from the annular groove, may be in a direction toward or away from the housing of the injection device.
In the preferred embodiment of the invention, a coil spring may be provided for urging the locking ring to the position where the annular cam surface faces the locking balls.
Furthermore, there may be provided means for determining the position to which the barrel can be inserted in the socket. Such means may comprise a shoulder of the barrel, adapted to abut the forward end of the barrel.
The mounting member defining the socket may have a piece of rubber tightly fitted in an aperture drilled therein, the piece of rubber being in frictional engagement with a portion of the peripheral surface of the barrel to prevent it from unintentionally turning around it""s axis relative to the socket.
As the locking ring is manually pushed against action of the coil spring to the position where the relieving surface is opposite to the locking balls in the ball retaining holes, they are movable radially outwardly toward the relieving surface so that the barrel can be removed from or inserted in the socket for charge or removal of a cartridge, and when ceasing the pushing of the locking ring, it is returned to its original position under action of the coil spring so that the annular cam surface will engage the locking balls to push radially inwardly them into the annular groove, thereby preventing the barrel from coming out of the socket. In this position, the barrel is rotatable around it""s axis so as to be capable of altering the orientations of the viewing window and cut surface of the needle secured to the barrel as desired. The piece of rubber apples enough braking to the barrel by frictional engagement with the outer peripheral surface of the barrel, to prevent it from unintentionally turning, thereby, maintaining the desired orientations of the viewing window and cut surface of the needle during injection.